Traction-motor control



Dec. 22, 1953 N. H. WILLBY 2,663,835

TRACTION-MOTOR CONTROL Filed March 30. 1951 Com-Gontrolln 6 bcdof hi'k To Auxiliary Brukn 000000000 oooo00 WIT ESSES M I INVENTOR as I! IB 2c M 2 RT 9 22 Norman H.WiHby.

. 2: 0i sw a" Flg. 2.

ATTORNEY Patented Dec. 22, 1953 UNITED STATES PATENT OFFICE TRACTION-MOTOR CONTROL Norman H. Willby, Irwin, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a. corporation of Pennsylvania Application March 30, 1951, Serial No. 218,320

15 Claims. (Cl. 318-249) My invention relates to traction-motor control-systems and apparatus, and it has particular relation to trolley-coach or bus equipment using a direct-current motor having both a series mainfield winding and a shunt maincield winding, on the same magnetic poles, the series winding being exclusively excited for motoring, and the shunt winding being exclusively excited for dynamic braking.

One feature of my invention is to provide an automatic acceleration-mechanisin using a limitrelay which has not only a series coil which is responsive to the motor-current, but also a shunt coil which is responsive to the voltage induced in the "hunt winding, or which is otherwise responsive to the rate of increase of the motor current in response to the step-by-step advance of the accelerating equipment, or any equivalent means to this end. in this way, I cause the limit-reiay to check the progress of the accelerating steps with greater certainty, thus preventing the skipping of acceleration-steps, which has heretofore been one of the major troubles of accelerating controllers.

A further object of my invention is to provide novel means for shutting off the shunt-field current when the coach has reached a speed low enough so that dynamic braking is no longer practical, using, for this purpose, a special shuntfield relay having a close coil which is energized across the line in response to a ready for braking condition, and also an auxiliary coil which is responsive to the voltage (or current) in the motor-armature, or which is otherwise responsive to the magnitude of a dynamic-braking quantity, so as U hold to the shunt-field relay in, during braking, and to release said relay upon the diminution of the dynamic-braking quantity below a predetermined magnitude.

With t -e foregoing and other objects in view, my invention consists in the apparatus, circuits, systems, combinations, parts, and methods of design and operation, hereinafter described and claimed, and illustrated in the accompanying drawing, wherein:

Figure 1 is a diagrammatic view of circuits and apparatus embodying my invention in a preferred illustrative form of embodiment, and

Fig. 2 is a similar View of a part of the apparatus, illustrating an alternative form of embodiment.

The equipment shown in Fig. 1 represents the electrical parts a trolley-coach, which is enirom positive and negative trolley-wires if and Ir through two trolley-poles 3 and 4, or

2 other current-collecting devices. The two trol icy-poles 3 and t energize a pair or" supply-line terminals Ti and T2, respectively, preferably through a. switching-means 5 which is interposed between at least one of the terminals Ti and its associated tro1ley-pole 3.

The trolley-coach is provided with a main dircct-current traction-motor having an ar 'ature A, a series n1ain-field winding is and a shun a n field winding '3, these two main-field windings being wound on the same poles. The series mainfieid winding 6 is connected in cries with the armature A through a reverser ii.

The acceleration of the main motor A accomplished by operating the motor as a straight or ordinary series motor which is brought up to speed by cutting out series resistances R5 to R3, in a conventional manner. When of the series resistance R! to R5 been out the motorspeed may be still further "ECEEELSSCI by one or more field-shunting steps whereby the series field t is shunted by a field-shunt consisting of a resistance R? and a choke-coil 8, which be connected, in whole or in part, in shunt across the seri s main-field winding Dynamic braking is accomplished by a disconnection of the main motor from the line, and the separate energization of the shunt fieid- "'inding 1, either across the line or across any other suitable direct-current source other than the armature-terminals oi the main motor. During this dynamic-braking operation, a suitable dynamic-or king load, shown as consisting of resistances RA and RE, is connected across the terminals of the motor-armature A.

In accordance with a known dynamic-braking system, the net exoitingwoitage which is impressed upon the shunt-field winding l is automatically reduced by the aino t of voltage-drop which is produced by the armature-current in the RB resistor, so as to automatically the motor-excitation when the hr""ing-cur t decreases, thus producing the e ite of a nOl/wlless type of dynamic braking, which produces an approximately constant tractive effort. In pram tice, the dynamic braking starts out at a high motor-speed, with a high armature-current and a low shunt-field excitation, as the motor speed decreases, the armature-current also de" creases and the shunt-field current automatically increases, so as to tend to increase the amount of dynamic braking which is produced by the motor. The amount or dynamic-braking tractive-eirort which is maintained may be pro-selected by the cutting out of more or less of a fieid- 3 resistance R3 to B5 c which is connected in series ith the shunt main-field winding 7 during dynamic braking.

In accordance with a known practice, trolley-coach equipment also includes an aurailiary direct-current motor, having an armature AX, and a series field-winding ii. This auxiliary motor is adapted to be connected across the line-terminals T! and T2 by any suitable switching-means E2. The auxiliary inotor AX is, or may be, used for any one or" a number of purposes which are more or less important to the successful operation of the main motor A, such as driving a blower (not shown) for cooling the resistors or even cooling the main motor itself, or driving an auxiliary generator (not shown) for battery-charging or for other auxiliary uses on the trolley-coach.

The controller-equipment for controlling the operation of the main traction-motor A includes four controllers which are shown at the bottom of Fig. 1. Reading backwardly, from right to left, these controllers include, first, a master controller M which is operated by a pedal 53; second, a brake-controller B which is operated by a pedal it; third, a cam-controller C which is illustrated as being operated by an air-engine consisting of two opposed cylinders C2 and C3; and finally a two-position power-brake changeover (P/B Ch. 0.) switch P, which is illustrated as being actuated by an air-engine having a single cylinder C1, which moves the changeover switch against the bias of a spring 15 which is adapted to return to the switch to its normal unactuated position.

Each of these four controllers M, B, C, and P is provided with a plurality of operating-positions and a plurality of contacts, the latter being designated by letter-suffixes, and the con tact-sequence being diagrammatically indicated, in each case, in the form of a sequence-chart wherein a closed position of any particular contact is indicated by a circle, in accordance with the usual convention. For convenience in finding the various contacts or" the several controllers, and as a convention for diagrammatically indicating the mechanical connection or association between the various contacts and the various controllers, I have used arrows, which have been chosen in lieu of dotted-line connections, as a convention for indicating the association without confusing the diagram with large numbers of dotted lines running between the various parts.

The illustrated control-circuits, for controlling the main traction-motor A during motoring and braking, may be traced as follows. Starting with the line-terminal Ti, the main motor-circuit includes, a first, a contactor Pa of the power-brake changeover-switch P, followed by the accelerating resistors R! to RE which are under the control of the cam-controller contacts Ca to Cg. Next comes the positive terminal it of the motor-armature A, followed by the armature and the negative armature-terminal H, the reverser 3, a conductor E8, the main or series coil 29 of a limit-relay LR, and finally a line-switch contact LS, which is connected to the negative line-terminal T2. The field-shunt R7 and 9 is adapted to be connected across the series mainfield winding ii by means of a controller-contact Ch which is connected between the negative motor-terminal H and a conductor 2i. Next comes the shunt-resistor R'l', which is shunted by a controller-contact Ci, followed by d the choke-coil 9 which is connected to the conductor E8.

The limit-relay LR is provided with a bachcontact 22, which is closed when the relay is deenergized or not sufficiently energized. This relay is biased toward its not-responsive or nonenergized position by means of a spring 23, which is stretched by a depression of the inaster-controlier pedal 53, as diagrammatically indicated by a mechanical connection in accordance with a known motor-coach controlsystem. According to my present invention, however, I provide the limit-relay LB with a second operating coil 25, or other operatingmeans which makes the limit-relay responsive to the sudden rates of increase of the current in the main rnotor A, during successive notches or positions of the accelcrating-controller C. As a convenient A eans for making the limit-relay LR responsive to the rate of increase oi the current in the main motor, I have illustrated the auxiliary relay-winding 25, in Fig. i, as being energized across the terminals of the shunt mainfield winding l, through a suitable resistance Ril which is connected in series with the auxiliary relay-coil 25.

In many trolley-coach installations, the main traction-motor is not operated back rardly except at very slow speeds, and for brief times, so that the operation of the limit-relay LR is not important during such conditions. However, in case the limit-relay operation is in1portant during reversed motor-connections, the improper response or t -e auxiliary limit-relay coil 25 may be avoided, either by the use of a serially connected rectifier 2% in series with said auxiliary coil 25, or by means of additional reverser-contacts 23, or both of these expedients may be used, or both omitted if they are not required.

The purpose of the auxiliary coil 2r; of the limit-relay LR is to give said relay a cumulative or added operating-impulse, in addition to the action of the main relay-coil 2%, whenever there is a sudden increase in the motor-current. A sudden increase in the motor-current produces a sudden increase in the main-field fillX, due to the series main-field winding 5, and this induces a voltage in the shunt main-field winding 71', which gives the desired impulse to the auxiliary coil of the limit-relay LR.

For dynamic-braking operation, the motorarmature A is shunted by means of a brakingresistor load-circuit, which may be traced from the positive motor-terminal it, through the braking-resistor RB to a conductor 39, thence through the bralring-resistor RA to a conductor 3i, and finally through a changeover-switch contact Pb to the negative motor-terminal i'l.

The energization of the shunt main-field winding '5 during dynamic braking is accomplished by a circuit which may be traced the positive line-terminal Ti, through the make-contact of a shunt-field contactor SFi, and thence hrough the field-resistors R2 and R9 which are respectively shunted by two shunt-field contactors and SP3, and then through the field resistance Riki which is cormected to the conductor Next comes the braking-resistor which is traversed by the motor-current during dynamic braking, and which is connected to the positive motor-terminal it. The shunt main-field winding '5 is connected between this positive motor-terminal it and the negative line-terminal T2 through the make-contact of a fourth shunt-field contactor SE4.

cc rding to my present invention, the braking-resistor RA (or any other portion of the braking-resistor load-circuit) is shunted by means of an auxiliary or holding coil 33 of a special shunt-field relay SFR. This relay is also provided with a main or close coil 34 which is connect :1 across the line-terminals TI and T2 through a brake-controller contact Ba and a resistor Bi The shunt-field relay SFR is provided with a intake-contact 35 which is in series with the energizing-circuits for the operating-coils of the four shunt-field contactors SP1 to SFQ.

The control-circuits for these four shunt-field contactors SF-i to SP5, may be traced as follows. Starting from the positive terminal of any suitable direct-current source, which may be a battery (not otherwise shown) carried by the trolley-coach, this shunt-field contactor-energizing circuit extends first through a brake-con: troller contact 13d, then a changeover-switch contact Po, then th SFR contact 35, and thence to a conductor The conductor 38 is directly connected to the operating-coils SF! and SEE of the shunt-field contactors SFI and SE4 respectively. The conductor 36 is also connected, through a brake-controller contact Bl), to the operating coil SP2 of the shunt-field contactor SFE. in like manner, the conductor 35 is connected, through a brake-controller contact 130, to the operating coil SP3 of the shunt-field contactor The circuit for the auxiliary mot: can be traced from the positive linc-conductor Tl, through the switching member !2, the armature AX, the series field i l and thence to a conductor 37. The circuit then continues, from the con=- ductor through a cam-controller contact Ci, to a conductor 38, and thence through the main coil 3% of an auxiliary relay or contactor X, and finally to the negative line-terminal T2. The contactor X has two make-contacts 4i and is.

As described and claimed in a companionapplication of Bernard J. Krings, Serial No. 219,847, filed April 7, 1951, the contactor X is provided with an auxiliary bucking or differential coil which is energized so as to be responsive to the rate of decrease of the current in the main motor A during motoring operation. In Fig. 1, this rate-of-decrease response is obtained by connecting the auxiliary coil 43 of the contactor X I across the series main-field winding 6, to take advantage of the fact that said series main-field winding develops, across its terminals, a voltage which is res onsive to the rate of change of the motor-current, during motoring, because of the reactance of this series main-field winding. Since the main need for the auxiliary buckingccil as on the contactor X is during weakenedfi-eld operation, I have shown, in Fig. 1, an energizing connection whereby the aforesaid buckingcoil 43 is connected across the conductors 2| and i8, so as to be energized only when the controllercontact Ch is closed. It will be understood, of course, that any equivalent bucking-coil energization might be used, whereby the contactor X is given a kick-out impulse, or a demagnetizing impulse, in response to a sudden decrease in the current flowing through the main motor A during the motoring operation, as would be obtained when there is an interruption in the power which is supplied to the line-terminals Ti and T2 of the trolley-coach.

As described in the aforesaid Krings application, the first contactor-contact 4] of the auxiliary contactcr X is connected across the. con,-

ductors 3! and 38, so as to be in parallel with the controller-contact G7, which is also an innovation which has been introduced in accordance with the Krinss invention.

The second contactor-contact 42 is used, in a somewhat conventional fashion, to condition a control-circuit 44-45 for motoring-operation when the auxiliary motor AX is properly energized for running. Since motoring operation should be permitted only in the off-position of the brake-controller B, the motor-operation control-circuit 4 is energized, say from the positive battery-terminal through the brakecontroller contact Be. When the motor-operation control-circuit M is thus energized, a branchcircuit through the master-controller contact IvIa, energizes the valve magnet-coil 45 of a standard valve V1, which admits compressed air to the cylinder C1 which actuates the power-brake changeover-switch P so as to move it from its braking position No. l, to its motoring position No. 2, thereby opening the braking-operation changeover-contacts Pb and Po, and closing the motoring-operation changeover-contact Pa which is in the motor-energizing circuit of the main motor A.

This master-controller contact Ma, which controls the changeover-switch P, is closed in response to the first movement of the master-controller pedal i3. At the same time, the master controller M closes a second contact Mb, which is connected between the circuit 15 and the operating coil LS of the line-switch LS, thus completing the energization-circuit for the main motor A, with all of the starting-resistance Rl to R5 in series with the motor-armature. lhis happens in the N0. 1 position of the master-controller M, which closely follows an off-position in which the master-controller contacts are open.

When the master-controller pedal i3 is still further depressed, it puts the master-controller in its last position, which is marked position No. 2. This is a general term for any portion of all of the rest of the movement of the master-controller, after passing the brief No. 1 position. In the No. 2 position, the master-controller M keeps its contacts Ma and Mb closed, and closes its third contact Me, which is connected between the conductor 45 and a conductor 55. This conductor 56 energizes a valve magnet-coil 51 of a standard valve V2, which admits compressed air to the cylinder C2, the function of which is to drive the cam-controller C in the advancing or forward direction. The cam-controller C cannot move forward, however, as long as the return-movement cylinder C3 is energized, which is normally the case because it is associated with an inverted magnet valve V3 which, in its normal or deenergized position, admits compressed air to the return-movement cylinder C3.

The inverted valve V3 provided with a magnet-coil 52, which is energized, in series with the limit-relay bacr contaot from the previously mentioned conductor so. Since the limitrelay LR is initially dcenergized, the first advance of the master-controller into position No. 2 results in the energization of the inverted-valve magnet-coil 52, simultaneously with the energization of the standard-valve magnet-coil 5!, so that the cam-controller 0 immediately begins to be pushed forward by its air-engine. The cam-controller C then acts as a multi-step acceleratormeans, for making progressive changes in the electrical energization of the main traction-motor A, for increasing its speed. At the same time,

accesse 7 the cam-controller C acts as a sequence-determining means for controlling the sequence of these motor-accelerating steps.

The cam-controller C, if its air-engine magnetcoils i and 52 were left continuously energized, would complete its advance-movement in 2% seconds, or whatever other time the apparatus is set for. However, it will be noted that the advance-movement of the air-engine which controls the cam-contactor C is under the control of the back-contact of the limit-relay LR, so that, as soon as the acceleration-control of the main traction-motor A has progressed far enough to make the motor-current overcome the setting of the limit-relay LR, the limit-relay hack-com tact o ens, thereby deenergizing the inverted valve V2 and admitting compressed air to the return-movement cylinder C3, thereby locking the two cylinders C2 and C3 against each other, so that the cam-controller is held still at this time. The advance-step oi the accelerationsequence is not taken until the motor has re mained on the step at wh ch the limit-relay LR picked long enough for its motor-current to subside below the dropout-setting of the limitrelay LR, due to the gradual further acceleration of the motor while is on this position or notch.

The setting of the limit-relay LR is under the control or" the operator, because it is dependent upon the amount by which the master-con roller pedal is is depressed. In this manner, the operator has control over the rate at which the trolleycoach is accelerated, or the maximum permissible motor-current which is permitted to flow in the main traction-motor A.

ihe return-circuits for the line-switch coil LS, and for the two valve magnet-coils 5i and 52 of the cam-controller C, are through a conductor I, which is connected to the negative hattery-terminal through a cam-controller contact 3. which is shunted by auxiliary maizecontact on the line-switch LS. The four shunt-field contactor coils SFl to SEQ, and the valve magnet-coil or" the power-brake changeover-switch P, all have their return-circuits directly connected to the negative battery-terminal The operation of the trolley-coach control-systern which is shown in Fig. i will be more or less apparent from the sequence-charts which constitute the diagrammatic representation of the four controllers ill, B, C, and P, and from the preceding descriptions. ihe operation may be summarized, however, as follows, with special emphasis on novel features of the invention.

Whenever the master-controller M is in its off-position, the power-bralse changeover-switch P is its deenergized or No. 1 position, in which the main motor A is disconnected from the line terminal Ti by the open changeover-contact Pa, and in which the two brake-position changeovercontacts Pb and Po are both closed. The changeover-contact Pb connects the two braking resistors RA and RB across the armature-circuit iE--il of the main motor, while the changeovercontact Po partially prepares the energizing-circuit for the four shunt field contactor-coils SFE to SF i.

If, now, the master-controller pedal is is depressed, the master controller M, through its contacts ll/lo and Mt, will first energize the changeover-switch P and the line-switch LS, thus energizing the main motor A across the line-terminals T! and T2, through the closure of the contacts Pa and LS. When the master-con- 8... troller M is advanced into its position No. 2, the acceleration of the main motor then proceeds in the usual manner, except for my special limitrelay energization. The second limit-relay coil 25 has the efiect of increasing the limit-relay excitation in response to the sudden rate of increase of the motor-current, at each moment when an advance-step or notch is taken in the acceleration-control of the main-motor. This additional excitation-impulse lasts but a moment, but it has the advantage of making the limit-relay LR pick up with greater certainty and promptness, when the main motor-current is about to reach the value for which the limitrelay is set. This improved limit-relay is thus very efiective in preventing the skipping of notches, or advance-steps in the acceleration of the main motor, which was one of the major troubles of the described type of accelerationcontroller when it was heretofore used with a conventional limit-relay having only a series operating-coil in series with the current of the main motor A.

The relative strengths of the limit-relay seriescoil 25 and the limit-relay auxiliary coil 25 may be adjusted over considerable limits. By making the auxiliary coil 25 relatively weak, its transient impulses due to successive adVance-notchings of the multi-step accelerator-control will be sufficiently weak to have no effect upon the operation of the limit-relay LR until the motor-current approaches fairly close to its limiting value, which is set by the amount of depression of the master-controller pedal l3, and hence the amount of pull of the spring 23 which controls the setting of the limit-relay LR.

in this way, the forward movement of the camcontroller or accelerator C may be left undisturbed until a sufficient number of acceleratingnotches or positions have been passed, to cause the current in the main motor A to reach, say, of its desired maximum value, according to the rate of acceleration which is fixed by the position of the operator's master-controller pedal 53. After this current-value has been reached in the main motor, the series coil 253 of the limitrelay will have nearly enough energization to pick up the limit-relay, so that, on each succeeding notch, the additional energization which is provided by the shunt coil 25 of the limit-relay, in response to each current-increase when a new notch is reached, will cause the limit-relay LP: to pick up, one notch at a time, thus stopping the progression or advancement of the cam-controller or accelerator C each time a new notch or position is reached, thus permitting the subsequent dropout-action of the limit-relay LR to control the times at which additional one-step advances are to be made in the progress of the movement of the cam-controller C.

When the master-controller M is returned to its Off-position, its contacts Ma, lvib,'and Mo are all opened, thus opening the power-brake changeover-contact Pa, opening the line-switch contact LS, and at the same time deenergizing both of the magnet-coils 5i and 52 of the camcontroller C, so that the inverted valve V3 admits compressed air to the return-movement cylinder C3, while the standard valve V2 vents the advance-movement cylinder C2, thus causing the air-engine to return the cam-controller C to its No. 1 position. At the same time that the powerbrake changeover-contact Pa is opened, the changeover-contact Pb is closed, connecting the braking-resistors RA and RB across the armature-terminals l6 and ii, and the changeover- 9 contact P is closed, in the control-circuit for the shunt-field contacts SFi to set; but the shunt main-field Winding 1 is deenergized at this time, so that there is substantially no dynamic braking.

As soon as the lineas itch LS is dropped out, its auxiliary make-con ct 53 opens, thus dis connecting the control-circuit conductor T-- from the negative source-terminal This makes it impossible for the operator, by imme diately again moving his master-controller M to the full-on position, to again energize either the line-switch LS or the magnet-coils i and E2 of the air-engine of the cam-controller C, until the return-movement of the air-engine has returned the cam-controller C to a position which is sui ficiently close to its starting or low-speed posi tion, so that it will be safe to re-energize the main motor it without discomfort to the coachpassengers and Without undesirable mechanical strains on the equipment. During as many of the first positions of the cam-controller C as may thus be desirabl (the first two positions being indicated on the sequence-chart of this controller), the controllencontact Ck is closed, bein open in all subsequent positions of the can controller C. When the return-movement of the cam-controller C has reached such a low-speed position that the aforesaid contact Clc is closed, then the open make-contact 53 of the line-switch L5 is by-passed, and it then becomes possible for the operator to set up anew motor-operation of the main motor A, as is well known in the art.

My special shunt-field relay SF'R is normally energized, through its close winding 34, whenever the brakecontroller B is in its off-position, at which time the brake-controller contact Ba connects said close coil 34 across the lineterminals Ii-T2, or across whatever other direct-current source is used for exciting the shunt main-field winding '1 during the dynamic-braking operation of the main motor A. When this special shunt-field relay SFR is energized, it closes its make-contact 35 which partially energizes the control-circuit 35 for the shunt-field contactors SF! to SP4, by which I mean that it puts said control-circuit in readiness for being energized as soon as the brake-controller contact Bd closes.

If, now, the brake-controller pedal I4 is depressed while the main motor A is coasting, disconnected irom the line at Pa and LS, the first on-position of the brake-controller B will close the controller-contact Ed, thus energizing the control-circuit 35 since the contacts Po and 35 are already closed, as above described. The control-circuit conductor 35 will energize the first and last shunt-field contactors SFi and SP4. thus energizing the shunt main-field winding 1 of the main motor A. As soon as this shunt main-field winding '3 is energized, it causes the main motor to operate as a generator, building up a voltage across its armature-terminals i5 and ii, and supplying energy to the brake-resistance load RA and RE. The voltage-drop thus generated in the brake-resistance RA is applied to the hold coil 33 of the special shunt-field relay SFR, thus holding this relay energized, and keeping its contact 35 closed, notwithstanding the fact that its close coil 34 is cleenergized by reason of t -e opening of the brake-controller contact Ba at substantially the same time when the brake-controller contact. 3311 closed.

As previously stated, the voltage-drop due to the flow of the dynamic-braking armature-current through the braking-resistor R13 is in opposition to the line-voltage which is applied to the shunt main-field winding '5, so that the strength of the shunt-field excitation of the main motor A is automatically increased, as the armaturecurrent decreases as a result of the decreasing of the motor-speed, thus tending to hold the braking-traction more nearly constant. The amount of this brake-traction can be pro-selected by the amount of depression of the brake-pedal M, by moving the brake-controller B to either one of its three on-positions, thus selecting the amount of field-resistance R8 to R58 which is left in the circuit of the shunt main-field winding 7, thus controlling the excitation of the main motor during dynamic braking.

When the dynamic-braking current which is supplied by the motor-armature A drops to such a low value that dynamic braking is no longer practical, the reduced voltage-drop across the braking-resistor RA so far deenergizes the hold coil 33 of the special shunt-field relay SFR, that this relay drops out, and opens its make-contact 3.5, thus deenergizing all of the shunt-field contactors SF! to SP4, deenergizing the shunt mainfield winding '1, thereby preventin overheating of the shunt field-winding and unnecessary power-loss. It will be understood that the brakepedal l 4 is also used to control an auxiliary brake, as diagrammatically indicated by the connection 60, so as to be able to bring the coach to full standstill, and to hold the coach at standstill. This auxiliary brake may take any one of a number of forms, and may have any one of a number of diiierent control-systems (not shown), as is well understood in the art.

The special auxiliary relay or contactor X which is described and claimed in the Krings application is for the purpose of opening its con tact 42, so as to prevent a motoring operation, and also to prevent any advancement of the camcontroller C from its No. 1 position, in response to a power-off condition, and more particularly in response to a power-off condition which occurs while the main motor A is operating as a motor. This contactor X is provided with the usual main exciting winding or coil 39 which is energized by the current flowing through an auxiliary motor AX which performs such an important function (whatever that function may be) that its operation must be assured, before the commencement of a motoring-operation or the main motor A can be permitted.

It is extremely desirable, however, that means should be provided for opening or killing the motor-operation control-circuits if a power-interruption should occur during the motoring operation of the main motor A, and it is also desirable that this operation should be accomplished by the same relay or contactor X which is used to make sure that the auxiliary motor is op erating before the main motor is energized in the first place, thus avoiding the necessity for providing a separate power-off-responsive relay or contactor. Heretofore, this power-oi? response-function has usually been poorly or belatedly performed by the contactor when said contactor has been provided with only the one main energizing-coil 39, because, when a poweroff condition arises while the main meter A is motoring, the inertia of the main motor will cause it to operate as a series generator, supplying power, for awhile, to the auxiliary mo or AX, and thus preventing the auxiliary relay or contactor X from dropping out until the coach-speed has dropped to a rather low value.

By reason of the equipment of the special auz-ziliary relay or contactor X, with an auxiliary winding which is so connected as to produce a deenergizing effect in response to a sudden decrease in the current flowing through the main motor A, at the of a power-interruption, is now possible to so far neutralize the magneti- Fation produced by the main coil of this auxiliary relay X, as to cause said rela to drop out in response to every power-outage condition, not withstanding the regenerative power-feed haclz into the auxiliary motor from the main motor. The auxiliary contactor or relay X has a short dropout-time, which may be of the order of of a second. If a power-outage lasts less than that small length of time, an immediate reapplication of power to the main motor will generally not produce any objectionable effects. If a power-outage condition lasts longer than that, the improved auxiliary relay X will drop out, or be kicked out, thus opening not only the motoroperation control-circuits (at 52) but also opening the energizing-circuit of the main coil of this relay (at the contact iii).

This contact 45 is a new feature, which deen-- ergizes the auxiliary motor AX, and hence auxiliary relay or contactor until the can controller C has automatically moved heel: (or been moved back by the operator in case a manual control is used), to a suitable low-speed position, which again may be any low-speed position, and which is again illustrated as the No. 2 position, as indicated by the sequence-chart for the cam-controller contact Cy, which is connected in the auxiliary-motor cir uit in parallel with the contact l! of the auxiliary relay or contactor X.

It will be understood, from the foregoing description, that any means may be used, which will make the limit-relay LR responsive to the rate of increase of the current in the main motor A. In Fig. 2, I have shown an alternative energization-means to this end, which may he uses with a straight series motor A, that is, a motor having a series main-field winding but not the shunt main-field winding '5 which is shown in Fig. i. In Fig. 2, the variable-resistance acceleration of the motor A is simplified into an illustration of a variabl resistor R, while the fieldweakening control is the same as was shown in Fig. 1. The source of excitation for the auxiliary coil of the limit-relay LP, in 2 is taken directly from the terminals lli3 of the series inain-field winding s.

In Fig. 2, the acceleration-control is the same as in Fig. i, being under the control of the backcontact 222 of the limit-relay LR. Each time the acceleration-sequence is advanced one notch, there is an increment or increase in the motorcurrent, and he inductance of the series-field winding 6 causes a transient voltage-increase across the series-field terminals ii and 58, due to the hack-voltage induced by this field-inductance. This transient voltage increase, in response to advance-steps in the accelerationprocess, produces the same efiect, in 2, as it does in Fig. l, with the exception that, in Fig. 2, the auxiliary coil 25 of the limit-relay LR r ceives a steady-state voltage, as well as a transient voltage which is due to the rate of increase of the motor-current, so that it is necessary to use fewer turns in the main coil of the limitrelay LR in Fig. 2.

While I have illustrated my invention in only two illustrative forms of embodiment, I wish it ay means for at times iceinent of the mo itatici stopping the sequentia. tor-accelerating steps, and one ccel rating steps, lixrt= 2. A direct-current motor ha 1g 2. mainfield winding, multi'step aoceleratorcneans making progressive in the electrical 811-- ergization of the motor 2? increasing its speed, and for con rolling the sequence of the motor accelerating steps, lino t means for at times stopping the sequential of the motor-accelerating steps, and ex tion means for making said limi -relay means 1' pensive both to the magnitude or" the ll'iOt0i-C*"'1Elli and to the induced voltage in the series in iii-field winding.

A direct-current motor having both series and shunt main-field windings, motor-operation circuit-means for ueenergizing the shunt mainfield winding and for the series mainfield winding in series with the motor-armature across a pair of supply-line terminals during the motoring operation, multiste, acceleratormeans for making progressive in the electrical energization of the motor for increasing its speed during the motoring operation, and for controlling the sequence of the notoraccelerating steps, limit-relay means for at times stopping the sequential advancement of the motor-accelerating steps during the motoring operation, changeover circuit-means for energiz ing the shunt main-field winding from supply terminals other than the motor arinature terminals, and for substantially disconnecting the motor-armature from the supply-line terminals, and for connecting a braking-resistance load across the motor-armature, during dynamic braking, and excitation-means for making said limit-relay means r sponsive both to the magnitude of the motor-current and to the voltage induced in said shunt main-field Winding during the motoring operation.

4. A direct-current motor having both series and shunt main-field windings, motor-operation circuit-means for deenergizing the shunt mainfield winding and for energizing the series mainfield winding in series with the motor-armature across a pair of supply-line terminals during the motoring operation, multi=step acceleratormeans for making progressive changes in the electrical energization of the motor for increasing its speed during the motoring operation, changeover circuit-means for energizing the shunt main-field winding from supp1y-terminals other than the motor-armature terminals, and for substantially disconnecting the motor-armature from the supply-line terminals, and for conneoting a braking-resistance load across the motor-armature during dynamic braking, means responsive to a ready-for-braking condition for closing an interlocking control necessary for the establishment of dynamicbraking conditions and for releasing said interlocking control upon the establishment of dynamic-braking conditions, and means responsive to a predetermined magnitudeof a dynamic-braking quantity for holding said interlocking control and for releasing said interlocking control upon the diminution of said dynamic-braking quantity below a predetermined magnitude.

5. The invention defined in claim 4, in combination with field-current-limiting resistancemeans including a portion of said breaking-resistance load and a shunt-field resistance in series with said shunt main-field winding during said dynamic-braking conditions, the voltage drop due to the circulation of armature-current in said portion of the braking-resistance load being in opposition to the voltage of the supplyline terminals as applied to the shunt main-field Winding, and a brake-controller, movable under the control of an operator, for controlling the magnitude of the shunt-field resistance during the braking operation.

6. A direct-current motor, multi-step accelorator-means for making progressive changes in the electrical energization of the motor for increasing its speed, and for controlling the sequence of the motor-accelerating steps, limit-relay means for at times stopping the sequential advancement of the motor-accelerating steps, a master controller, movable under the control of an operator, for effecting the sequential operation of said accelerator-means and for controlling the setting of said limit-relay means in ac cordance with the movement of the master controller, and excitation-means for making said limit-relay means responsive both to the magnitude of an electrical quantity of the motor and to the rate of increase of said magnitude.

7. A direct-current motor having a series fieldwinding, multi-step accelerator-means for male ing progressive changes in th electrical energization of the motor for increasing its speed, and for controlling the sequence of the motoraccelerating steps, limit-relay means for at times stopping the sequential advancement of the motor-accelerating steps, a master controller, movable under the control of an operator, for efiecting the sequential operation of said accelerator-means and for controlling the setting of said limit-relay means in accordance with the movement of the master controller, and excitation-means for making said limit-relay means responsive to the induced voltage in the series field-winding.

8. A direct-current motor having a series fieldwinding, multi-step accelerator-means for making progressive changes in the electrical energization of the motor for increasing its speed, and for controlling the sequence of the motor-acceh crating steps, limit-relay means for at times stopping the sequential advancement of the motor-accelerating steps, a master controller, movable under the control of an operator, for effecting the sequential operation of said accelerator-means and for controlling the setting or" said limit-relay means in accordance with the movement of the master controller, and excitation-means for making said limit-relay means responsive both to the magnitude of the motorcurrent and to the rate of increase of said magnitude.

9. A direct-current motor having a series main field Winding, multi-step accelerator-means for making progressive changes in the electrical energization of the motor for increasing its speed, and for controlling the sequence of the motoraccelerating steps, limit-relay means for at times stopping the sequential advancement of the motor-accelerating steps, a master controller, movable under the control oi for effecting the sequential operation of said accelerator-means and for controlling the setting of said limit-relay means in accordance with the movement of the master control; r, and excitation-means for making said lircit-relay means responsive both to thev magnitude of the motorcurrent and to the induced voltage in the series main-field Winding.

10. A direct-current motor having both series and shunt main-field windings, motor-operation circuit-means for deenergizing the shunt mainfield winding and for energizing the series mainfield winding in series with the motoi armature across a pair of supply-line te "minals during the motoring operation, multi-step acceleratormeans for making progressive changes in the electrical energization of the motor for increasing its speed during the motoring operation, and for controlling the sequence or" the motor-accelerating steps, limit-relay means for at times stopping the sequential advancement of the motor-accelerating steps during the motoring operation, changeover circuit-means for energizing the shunt main-field winding from supplying terminals other than the motor-armature terminals, and for substantially disconnecting the n1otorarmature from the supply-line terminals, and for connecting a brakinguesistanc load across the motor-armature, during dynamic braking, a master controller, movable underthe control of an operator, for eiifecting the sequential operation of said accelerator-means and for controlling the setting of said limit-relay means in accordance with the movement of the master controller, and excitation-means for .ialzing said limit-relay means responsive both to. the magnitude of the motor-current and to the voltage induced in said shunt main-field Winding during the motoring operation.

11. The invention as defined in claim 10, in combination with field-current-limiting resistance-means including a portion of said brakingresistance load and a shunt-field resistance in series with said shunt main-field winding during said dynamic-braking conditions, the voltageclrop due to the circulation of armature-current in said portion of the braking-resistance load being in opposition to the voltage of the supply line terminals as applied to shunt main-field winding, and a brake-controller, movable under the control of an operator, for controlling the magnitude of the shunt-field resistance during he braking operation.

12. The invention as defined in claim 11, in combination with means responsive to a readyfor-braking condition for closing an interlocking control necessary for the establishment of dynamic-braking conditions and for releasing said interlocking control upon the establishment of dynamic-braking conditions, and means responsive to a predetermined magnitude of a dynamicbraking quantity for holding said interlocking control and for releasing said interlocking control upon the diminution of said dynamic-braking quantity below a. predetermined magnitude.

13. A direct-current motor having both series and shunt main-field windings, motor-operation circuit-means for deenergizing the shunt mainfield winding and for energizing the series mainfield winding in series with the motor-armature across a pair of supply-line terminals during the motoring operation, mu1ti-step acceleratormeans for making progressive changes in the electrical energization of the motor for increasing its speed during the motoring operation, changeover circuit-means for energizing the shunt main-field winding, and for substantially disconnecting the motor-armature from the supply-line terminals, and for connecting a braking-resistance load across the motor-armature, during dynamic braking, means responsive to a ready-forbraliing condition for closing an interlocking control necessary for the establishment of dynamicbraking conditions and for releasing said interlocking control upon the establishment of dynamic-bralzing conditions, and means responsive to a predetermined magnitude of a dynamic= braking quantity for holding said interlocking control and for releasing said interlocking control upon the diminution of said dynamic-braking quantit r below a predetermined magnitude.

14. The invention as defined in claim 13, in combination with field-currentlimiting resistance-means including a portion or" said brakingresistance load and a shunt-field resistance in series with said shunt main-field Winding during said dynamic-braking conditions, the Voltagedrop due to the circulation of armature-current in said portion of the brakingwesistance load being in opposition to the energizing voltage which is applied to the shunt main-field winding, and a brake-controller, movable under the control of an operator, for controlling the magnitude of the shunt-field resistance during the braking operation.

15. A direct-current motor having both series and shunt main-field windings, motor-operation circuit-means for deenergizing the shunt mainfield winding and for energizing the series main field. winding in series with the motor-armature across a pair of supply-line terminals during the motoring operation, multi-step accelerator-means for making progressive changes in the electrical energization of the motor for increasing its speed during the motoring operation, changeover circuit-means for energizing the shunt main-field winding, and for substantially disconnecting the motor-armature from the supply-line terminals, and for connecting a braking-resistance load across the motor-armature, during dynamic braking, field-current-limiting resistance-means including a portion of said braking-resistance lOad and a shunt-field resistance in series with said. shunt main-field winding during said dynamic-braking conditions, the voltage-drop due to the circulation of armature-current in said portion of the braking-resistance load being in opposition to the energizing-voltage which is applied to the shunt main-field winding, a brakecontroller, movable under the control of an operator, for controlling the magnitude of the shuntfield resistance during the braking operation, means responsive to the ofi-position of said brake-controller for closing an interlocking control necessary for the establishment of dynamicbraking conditions and for releasing said interlocking control upon the actuation of said brakecontroller, and means responsive to a predetermined magnitude of a dynamic-braking quantity for holding said interlocking control and for releasing said interlocking control upon th diminution of said dynamic-braking quantity below a predetermined magnitude.

NORMAN H. WILLBY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,126,163 Cooper Jan. 26, 1915 1,662,243 Evans Mar. 13, 1928 1,703,487 Jones Feb. 26, 1929 1,871,697 James Aug. 16, 1932 2,073,382 Trofimov Mar. 9, 1937 2,561,782 Bunyan July 24, 1951 

